This invention relates to a mechanical rotary seal used between a submersible pump and a relatively rotating shaft to effect a tight fluid seal between the pump housing and the rotating shaft. More specifically, the invention relates to a mechanical rotating seal comprising a locking mechanism for locking onto the rotary shaft.
Mechanical rotating seals are used to effect a tight seal between a rotating shaft and the housing of a submersible pump at the point where the rotating shaft enters the pump housing. Mechanical rotating seals are employed in a variety of submersible pumps used in water treatment facilities and mining operations Rotating seals undergo extraordinary stress created by the friction and rotation of the shaft as it enters the housing. Various materials and structural designs have been utilized to both manage and reduce stress to the seal. These seals wear out quickly and allow foreign matter into the housing thereby requiring frequent service and replacement. Slippage between the parts of the seal occurs during rotation and is also a cause of extensive wear on the seals.
Different forms of shaft sealing mechanisms have been utilized to attempt to keep foreign material from leaking into pump equipment. When foreign materials get into the pump equipment, shaft wear, corrosion, and degradation can occur. Seal mechanisms in current use are often comprised of two seal rings with opposing sealing faces, one face rotating relative to the other, to create a continuous, tight seal. Often coil springs are used to provide continuous contact between the diametrically opposed cooperative seal faces. Different prior art have used different inner structure and arrangements to improve sealing quality and reduce wear. Koss, U.S. Pat. No. 3,140,129, discloses inner and outer rings for receiving a bearing assembly that contains a plurality of roller bearings. The bearing assembly uses race rings to provide a track to maintain the individual bearings in their place. Koss describes a bearing assembly system using tight fitting rings and lubricant to accomplish the seal. Also disclosed is the use of annular sealing rings with a large diameter inserted into retaining grooves on the race rings to create the seal inside the assembly. The bearings are constructed of a low friction material.
A self-contained rotary mechanical seal is disclosed in Thurber, U.S. Pat. No. 4,213,618. The seal includes an annular lug holder that is secured to the rotating shaft by set screws. A belleveville washer assembly is disposed within the lugs. Hadley, in U.S. Pat. No. 3,672,689 teaches a mechanical seal assembly comprising a shaft seal for effecting a seal between a wall member and a rotatable shaft which prevents the flow of pressurized fluid from one to the other side of the wall. A removable slipper sleeve enables the seal assembly to be used in either a balanced or an unbalanced application. Means such as screws engage the parts of the seal to prevent the parts from rotating relative to each other.
Murphy, U.S. Pat. No. 6,017,036, discloses a split seal mechanism using packing material such as cotton fiber or fiberglass to create the seal. The seal must be frequently serviced to replace the material. Entrikin, U.S. Pat. No. 4,634,134, discloses a seal system composed of two fixed rings. The first is fixed with respect to a wall, and the second is fixed with respect to the shaft. The two seal members are oriented with a bushing in between them to stop the entry of material into the area between them and create the resulting seal.
Altnau, U.S. Pat. No. 4,289,320, discloses a conical spring used inside of a rubber bellows, which engages the outside of the base wall, to force the seal ring into engagement with an upper bronze ring. The upper ring is contained inside of a retainer member that is fixed to the outside of a rotating shaft. Orlowski, U.S. Pat. No. 5,865,441, discloses a positive pressure sealing mechanism that can run without grease or lubricant because of fluid pressures asserted against compartments inside of the sealing mechanism. The chamber is fluid tight, but the individual compartments are not. Fluid pressure can move between the different compartments.
Ostrowski, U.S. Pat. No. 5,947,479, discloses a mechanical end face seal using a pair of rotating rings having seal faces in contact with one another. An annular diaphragm is used to apply positive tension between the housing and shaft. The force made by the installed annular diaphragm is made to match the force created by liquid pressures against the seal during operation. Dahlheimer et al., U.S. Pat. No. 5,123,660, discloses a rotary face seal using a contoured diaphragm in an elastomeric boot. A tubular insert of metal is molded into the boot to insure a seal on the shaft. Also, a washer shaped insert is described with raised lands on one of the faces and is embedded in the seal washer to bring all the parts into alignment.
A self-contained rotary mechanical seal is disclosed in Thurber, U.S. Pat. No. 4,213,618. The ""618 seal is mounted on a rotating shaft to form a seal between the shaft and the structure on a housing through which the shaft extends. The seal includes an annular lug holder to be secured to the shaft by set screws. A plurality of lugs extend from the lug holder parallel to the shaft. Times extend circumferentially from the ends of the lugs concentric to the axis of the lug holder. Belleville washer assemblies are disposed within the lugs. In U.S. Pat. No. 3,672,689, Hadley discloses a shaft seal for effecting a seal between a wall member and a rotatable shaft A seat is attached to the wall and presents a face to a rotating face of loaded seal assembly so as to present movable seal faces which engage each other as rotation occurs. Fasteners such as screws attach the seal to the rotating shaft.
One problem incurred by mechanical seal devices in the prior references is slippage that occurs between the various component parts as the mechanical seal rotates in conjunction with the rotating shaft. Such slippage increase wear and tear on the seal, increases down time for repair and replacement and decreases sealing capacity.
One objective of this invention is to provide a seal for rotating equipment that reduces leakage and avoids contamination by reducing slippage of the component parts. Accordingly, a mechanical rotary seal is provided that produces a positive drive force so that all components of the seal rotate in unison with the rotating shaft. The mechanical rotating seal of the present invention effects a tight fluid seal between a submersible pump housing and a rotating shaft entering the submersible pump housing when the mechanical rotary seal is engaged with a stationary seal or element within the submersible pump housing. In one preferred embodiment, the mechanical rotary seal comprises a seal housing, a retainer having a seal face and a coil spring between the seal housing and the retainer. Preferably, the seal housing comprises two or more retaining flanges. The seal housing along with its retaining flanges define a compartment to receive the coiled spring and the retainer. In one preferred embodiment, the retainer comprises a rim defining two or more notches for engaging the rim with the retaining flanges. One side of the retainer comprises a seal face adapted to rotate against the stationary seal face located in the pump housing. A disk is positioned between the retainer and the coil spring mounted within the compartment. One end of the coil spring abuts against the disk so that, when compressed, the spring provides a pressure force against the disk that is translated to the retainer thereby providing a pressure force for maintaining contact between the seal face and the stationery element when the mechanical rotary seal is rotating. In this way, new wear material is continuously present at the interface between the rotating seal face on the retainer and the stationery seal face.
Preferably, a retaining clip abuts the back of the seal housing. The retaining clip can comprise a flexible metal adapted to mount the rotating shaft under tension to maintain the position of the mechanical rotating seal on the rotating shaft and to provide a positive drive force so that the seal housing, the retainer, the disk, the spring and the retaining clip rotate in unison. The seal housing, the retainer, the disk, the coil spring and the retaining clip are configured to be coaxially disposed about the rotating shaft so that, when the mechanical rotary seal is mounted within the pump housing, the seal face is in tight sealing engagement with the stationary element.
In one preferred embodiment, the seal housing encloses the retainer, the disk and the coil spring when the rim is engaged with the retaining flanges prior to engagement with the stationery face. Alternatively, the rim can be spaced away from the retaining flanges when the seal face is in sealing engagement with the stationery face.
In another embodiment of the mechanical rotary seal for effecting a tight fluid seal the rotating shaft defines a shaft socket. The mechanical rotary seal of this embodiment comprises a seal housing, a retainer and a coil spring. The coil spring has a forward end and a rearward end, the rearward end positioned within the seal housing and the forward end positioned within the retainer. The seal housing can comprise a forward section and a rear section, the rear section forming a ridge and the ridge, cooperating with the inner segment, defines a socket. A seal face can be fitted within a forward surface of the retainer.
In this embodiment, a ball in slidable engagement with an annular retaining spring is positioned within the socket of the seal housing when the socket is aligned with the shaft socket on the rotating shaft. Preferably, the annular retaining spring is sized to fit snugly over the rotating shaft. The ball and annular retaining spring are adapted to maintain the position of the mechanical rotating seal when the ball is mounted within the shaft socket of the rotating shaft and provide a positive drive force so that all component parts of the mechanical seal rotate in unison thereby reducing slippage. Preferably, the seal housing, the retainer, the seal face, the coil spring and the annular retaining spring are adapted to be coaxially disposed about the rotating shaft so that the positive drive force is exerted causing the seal housing, the retainer, the seal face, the coil spring and the annular retaining spring to rotate in unison with the rotating shaft when the ball is seated within the shaft socket of the rotating shaft.